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libc++: perform configuration checks with -nodefaultlibs

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We're compiling libc++ with -nodefaultlibs, so we should also pass this
option during the configuration checks to ensure those checks are
consistent with the actual build.

The primary motivation here is to ease cross-compilation against a
non-standard set of C++ libraries. Previously, the configuration checks
would attempt to link against the standard C++ libraries, which would
cause link failures when cross-compiling, even though the actual library
link would go through correctly (because of the use of -nodefaultlibs
and explicitly specifying any needed libraries). This is more correct
even ignoring the motivation, however.

Patch by Shoaib Meenai!

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@280015 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Saleem Abdulrasool
2016-08-29 21:33:37 +00:00
parent 3ec6b84545
commit eb930a502c
2 changed files with 33 additions and 5 deletions
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5
cmake/Modules/CheckLibcxxAtomic.cmake
View File

@@ -9,10 +9,13 @@ INCLUDE(CheckCXXSourceCompiles)
function(check_cxx_atomics varname)
set(OLD_CMAKE_REQUIRED_FLAGS ${CMAKE_REQUIRED_FLAGS})
set(CMAKE_REQUIRED_FLAGS "-std=c++11 -nostdinc++ -isystem ${LIBCXX_SOURCE_DIR}/include")
set(CMAKE_REQUIRED_FLAGS "-nodefaultlibs -std=c++11 -nostdinc++ -isystem ${LIBCXX_SOURCE_DIR}/include")
if (${LIBCXX_GCC_TOOLCHAIN})
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} --gcc-toolchain=${LIBCXX_GCC_TOOLCHAIN}")
endif()
if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
endif()
check_cxx_source_compiles("
#include <cstdint>
#include <atomic>

33
cmake/config-ix.cmake
View File

@@ -1,5 +1,34 @@
include(CheckLibraryExists)
include(CheckCXXCompilerFlag)
check_library_exists(c fopen "" LIBCXX_HAS_C_LIB)
if (NOT LIBCXX_USE_COMPILER_RT)
check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXX_HAS_GCC_S_LIB)
endif()
# libc++ is built with -nodefaultlibs, so we want all our checks to also
# use this option, otherwise we may end up with an inconsistency between
# the flags we think we require during configuration (if the checks are
# performed without -nodefaultlibs) and the flags that are actually
# required during compilation (which has the -nodefaultlibs). libc is
# required for the link to go through. We remove sanitizers from the
# configuration checks to avoid spurious link errors.
check_cxx_compiler_flag(-nodefaultlibs LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
if (LIBCXX_SUPPORTS_NODEFAULTLIBS_FLAG)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -nodefaultlibs")
if (LIBCXX_HAS_C_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES c)
endif ()
if (LIBCXX_USE_COMPILER_RT)
list(APPEND CMAKE_REQUIRED_LIBRARIES -rtlib=compiler-rt)
elseif (LIBCXX_HAS_GCC_S_LIB)
list(APPEND CMAKE_REQUIRED_LIBRARIES gcc_s)
endif ()
if (CMAKE_C_FLAGS MATCHES -fsanitize OR CMAKE_CXX_FLAGS MATCHES -fsanitize)
set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -fno-sanitize=all")
endif ()
endif ()
include(CheckLibcxxAtomic)
# Check compiler flags
@@ -14,9 +43,5 @@ check_cxx_compiler_flag(/GR- LIBCXX_HAS_NO_GR_FLAG)
# Check libraries
check_library_exists(pthread pthread_create "" LIBCXX_HAS_PTHREAD_LIB)
check_library_exists(c fopen "" LIBCXX_HAS_C_LIB)
check_library_exists(m ccos "" LIBCXX_HAS_M_LIB)
check_library_exists(rt clock_gettime "" LIBCXX_HAS_RT_LIB)
if (NOT LIBCXX_USE_COMPILER_RT)
check_library_exists(gcc_s __gcc_personality_v0 "" LIBCXX_HAS_GCC_S_LIB)
endif()